mgbinspect Posted December 29, 2009 Report Share Posted December 29, 2009 I inspected a 1951 home yesterday with a basement packed to the gills with all kinds of old tools and equipment. The owner, who had passed, apparently really liked to tinker. A couple things in particular came to the forefront as I tried to inspect this "tool time" museum: About two weeks ago - I forget which thread - I had raised the question, "Why aren't (or weren't) there more after-market gadgets attempting to wring the heat out of the exhaust from furnaces and boilers? Well, lo and behold I ran across two of 'em both chocked on about 6' of oil-fired boiler exhaust - both abandoned, of course, so the brain trust was apparently right, they aren't useful. Nonetheless, here they are: The first one was a heavy gauge steel heat exchanger incorporated into the exhaust system with blower and ducts (the ducts have been removed). Click to Enlarge 56.02 KB Click to Enlarge 53.09 KB Click to Enlarge 38.58 KB The second gadget was merely copper tubing coiled around the exhaust pipe with a metal jacket. I have no idea what he was doing with it, but it DID have a zone valve on it, so I don't think it had anything to do with a still... Click to Enlarge 43.67 KB Quote Link to comment Share on other sites More sharing options...
Inspectorjoe Posted December 29, 2009 Report Share Posted December 29, 2009 Those heat exchangers are fairly common around here, but I've never seen one that large. Here's my boilerplate: There is a heat recovery unit on the vent connector. These units cool the exhaust gasses, which can result in moisture condensing in the chimney, which can in turn cause deterioration of the chimney interior. The unit should be removed by a qualified HVAC technician. Quote Link to comment Share on other sites More sharing options...
mgbinspect Posted December 29, 2009 Author Report Share Posted December 29, 2009 ...These units cool the exhaust gasses, which can result in moisture condensing in the chimney, which can in turn cause deterioration of the chimney interior. The unit should be removed by a qualified HVAC technician.[/i] Thank much! Yeah, I gathered from the other thread that it wasn't a good idea, but this was the first one I had actually seen. Impressive construction, though. That's some serious steel! I suppose thermal mass was the aim? Quote Link to comment Share on other sites More sharing options...
Tom Raymond Posted December 29, 2009 Report Share Posted December 29, 2009 I like the 'heat recovery coil' concept far better than the 'heat exchanger' even if the HX construction is more impressive. To bad his coil is so short, another 20' or so and he might have actually scavenged some heat. Then again, maybe it's best that little experiment failed or else the chimney might have. Tom Quote Link to comment Share on other sites More sharing options...
Inspectorjoe Posted December 29, 2009 Report Share Posted December 29, 2009 That's some serious steel! I suppose thermal mass was the aim? I don't know. In addition to not having seen one that large, I've never seen one constructed of welded plate like that. Maybe it was insurance against the thing rusting out and dumping exhaust gasses into the basement. This is more like what I typically see - much lighter construction. This particular one handled both the water heater and the boiler. The problem of the smaller vent being below the larger one aside, venting both into that confined and obstructed box couldn't be good. Click to Enlarge 52.34 KB Here's a different type, without a heat exchanger. It's just a fan in an enclosure that surrounds the vent connector. Click to Enlarge 40.99 KB Quote Link to comment Share on other sites More sharing options...
Rob Amaral Posted December 29, 2009 Report Share Posted December 29, 2009 Junk any of those "grab the heat from the exhaust' gizmos... "Very 70's"... They can screw up your chimney flue, chimney top and your heating equipment from exhaust condensate dripping back... Quote Link to comment Share on other sites More sharing options...
mgbinspect Posted December 29, 2009 Author Report Share Posted December 29, 2009 I'm no HVAC guy by any means, but to look at one and imagine the big picture, the heat transfer rate has to be minuscule. How much heat can one of these things capture in one foot with the volume of air that 's moving through it via a fan? I suppose had they been able to run a computer model, they'd have abandoned the project while it was still in design phase. Quote Link to comment Share on other sites More sharing options...
Bill Kibbel Posted December 30, 2009 Report Share Posted December 30, 2009 I've seen all kinds of efforts to extract some extra heat, but this one just made me laugh. Click to Enlarge 45.98 KB The boiler was set several inches above the basement floor. There were little fans blowing air from under the boiler. Quote Link to comment Share on other sites More sharing options...
mgbinspect Posted December 30, 2009 Author Report Share Posted December 30, 2009 Now that is funny... How Christmassy! Quote Link to comment Share on other sites More sharing options...
Tom Raymond Posted December 30, 2009 Report Share Posted December 30, 2009 B-E-A-yootiful! Tom Quote Link to comment Share on other sites More sharing options...
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